0.3 mls blood to be obtained from 24 infants with herpesvirus infections and analyzed for T cell subsets and activation. Further samples (maximum 5) will be analyzed at 1 wk.-1 mo. intervals on infants whose first samples are abnormal. Control samples will be obtained from 10 uninfected infants and infants receiving blood transfusions. Results will be analyzed to test the hypothesis that herpesvirus infection activates T8+ lymphocytes and increase their number.